Sai A Sai A
Updated date Feb 07, 2024
In this blog, we will learn how to convert RGB colors to HCY colors using PHP. This blog provides step-by-step explanations, code samples, and outputs.


Colors are everywhere around us, and understanding how computers interpret and manipulate them is essential in various fields like graphic design, web development, and image processing. One fundamental aspect of working with colors is converting between different color models or color spaces. In this blog, we will focus on converting colors from the RGB (Red, Green, Blue) color model to the HCY (Hue, Chroma, Luminance) color model using PHP.

RGB and HCY Color Spaces

Before exploring the conversion process, let's understand the RGB and HCY color spaces.

RGB Color Space:

RGB is an additive color model where colors are created by combining different intensities of red, green, and blue light. Each color component ranges from 0 to 255, representing the absence (0) or full intensity (255) of that color.

HCY Color Space:

HCY is a cylindrical representation of colors, consisting of Hue, Chroma, and Luminance components. Hue represents the type of color (e.g., red, blue, green), Chroma represents the purity or saturation of the color, and Luminance represents the brightness of the color.

Converting RGB to HCY in PHP

Now, let's write a PHP function to convert RGB values to HCY values.

function rgb_to_hcy($r, $g, $b) {
    // Normalize RGB values
    $r = $r / 255;
    $g = $g / 255;
    $b = $b / 255;

    // Calculate maximum and minimum values
    $max = max($r, $g, $b);
    $min = min($r, $g, $b);

    // Calculate Chroma
    $chroma = $max - $min;

    // Calculate Hue
    if ($chroma == 0) {
        $hue = 0; // Undefined
    } else {
        switch ($max) {
            case $r:
                $hue = 60 * fmod((($g - $b) / $chroma), 6);
            case $g:
                $hue = 60 * (($b - $r) / $chroma + 2);
            case $b:
                $hue = 60 * (($r - $g) / $chroma + 4);

    // Calculate Luminance
    $luminance = ($max + $min) / 2;

    return array($hue, $chroma, $luminance);

// Example usage
list($hue, $chroma, $luminance) = rgb_to_hcy(255, 0, 0);
echo "Hue: $hue, Chroma: $chroma, Luminance: $luminance";


Hue: 0, Chroma: 1, Luminance: 0.5
  • We first normalize the RGB values to the range [0, 1].
  • Then, we calculate the maximum and minimum values among the RGB components to determine the Chroma.
  • Hue is calculated based on the maximum RGB component and the Chroma value.
  • Luminance is simply the average of the maximum and minimum RGB values.


In this blog, we have explored the conversion of RGB to HCY color spaces using PHP. Understanding color spaces and their conversions is important for various applications, from image processing algorithms to creating visually appealing designs.

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